Medical devices for renal nerve ablation

ABSTRACT

Medical devices and methods for making and using the same are disclosed. An example medical device may include a medical device for renal nerve ablation. The medical device may include an elongate shaft having a distal region. An expandable member may be coupled to the distal region. A plurality of electrodes may be coupled to the expandable member and a single conductive member may be coupled to each electrode. Where one of the plurality of electrodes is active, the remaining electrodes may be inactive and act as ground or return electrodes. The electrode of the plurality of electrodes that is active may change over time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 61/841,669, filed Jul. 1, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to medical devices for renal nerve ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includea medical device for renal nerve ablation. The medical device mayinclude an elongate shaft having a distal region. An expandable membermay be coupled to the distal region. A plurality of electrodes may becoupled to the expandable member. A single conductive member may beconnected to each of the electrodes, where each of the connectedconductive members are capable of powering the electrode to which theconductive trace is connected. When one of the plurality of electrodesis active, the remaining unpowered electrodes act as ground electrodes.

Another example medical device for renal ablation may include anelongate shaft having a distal region. An expandable balloon may becoupled to the distal region. A plurality of electrodes may be coupledto the expandable member. A plurality of conductive traces may becoupled to the elongate shaft and a single conductive trace of theplurality of conductive traces is connected to each of the electrodessuch that each of the connected single conductive traces is capable ofpowering the electrode to which the single conductive trace isconnected. When one of the plurality of electrodes is active, one ormore of the plurality of electrodes act as a ground electrode.

Methods for ablating renal nerves are also disclosed. An example methodmay include providing a medical device. The medical device may includean elongate shaft having a distal region. An expandable member may becoupled to the distal region. Two or more electrodes may be coupled tothe expandable member. The medical device may include a plurality ofconductive traces and a single conductive trace may be connected to eachof the two or more electrodes. The method may also include advancing themedical device through a blood vessel to a position within a renalartery, expanding the expandable member, activating one of the two ormore electrodes, and maintaining the remaining electrodes of the two ormore electrodes as inactive to act as ground electrodes.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of an illustrative medical device;

FIG. 2A is a schematic side view of a portion of an illustrative medicaldevice;

FIG. 2B is schematic cross-sectional view taken through line 2B-2B inFIG. 2A;

FIG. 3A is a schematic side view of a portion of an illustrative medicaldevice;

FIG. 3B is schematic cross-sectional view taken through line 3B-3B inFIG. 23;

FIG. 4A is a schematic side view of a portion of an illustrative medicaldevice;

FIG. 4B is schematic cross-sectional view taken through line 4B-4B inFIG. 4A;

FIG. 5A is a schematic side view of a portion of an example medicaldevice;

FIG. 5B is schematic cross-sectional view taken through line 5B-5B inFIG. 5A;

FIG. 6 is a schematic side view of a portion of an illustrative medicaldevice;

FIG. 7A is a schematic side view of a portion of an illustrative medicaldevice;

FIG. 7B is schematic cross-sectional view taken through line 7B-7B inFIG. 7A; and

FIG. 8 is schematic flow diagram showing an illustrative method of usinga medical device.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Certain treatments are aimed at the temporary or permanent interruptionor modification of select nerve function. One example treatment is renalnerve ablation, which is sometimes used to treat conditions such as orrelated to hypertension, congestive heart failure, diabetes, or otherconditions impacted by high blood pressure or salt retention. Thekidneys produce a sympathetic response, which may increase the undesiredretention of water and/or sodium. The result of the sympatheticresponse, for example, may be an increase in blood pressure. Ablatingsome of the nerves running to the kidneys (e.g., disposed adjacent to orotherwise along the renal arteries) may reduce or eliminate thissympathetic response, which may provide a corresponding reduction in theassociated undesired symptoms (e.g., a reduction in blood pressure).

While the devices and methods described herein are discussed relative torenal nerve ablation and/or modulation, it is contemplated that thedevices and methods may be used in other treatment locations and/orapplications where nerve modulation and/or other tissue modulationincluding heating, activation, blocking, disrupting, or ablation aredesired, such as, but not limited to: blood vessels, urinary vessels, orin other tissues via trocar and cannula access. For example, the devicesand methods described herein can be applied to hyperplastic tissueablation, cardiac ablation, pulmonary vein isolation, pulmonary veinablation, tumor ablation, benign prostatic hyperplasia therapy, nerveexcitation or blocking or ablation, modulation of muscle activity,hyperthermia or other warming of tissues, etc.

FIG. 1 is a schematic view of an example renal nerve modulation system10. System 10 may include a renal nerve ablation medical device 12. Therenal nerve ablation medical device 12 may be used to ablate nerves(e.g., renal nerves) disposed adjacent to the kidney K (e.g., renalnerves disposed about a renal artery RA). In use, renal nerve ablationdevice 12 may be advanced through a blood vessel such as the aorta A toa position within the renal artery RA. This may include advancing therenal nerve ablation device 12 through a guide sheath or catheter 14.When positioned as desired, the renal nerve ablation device 12 may beactivated to activate one or more electrodes (not shown in FIG. 1). Thismay include coupling renal nerve ablation medical device 12 to agenerator or controller 16 so as to supply the desired activation energyto the electrodes. For example, renal nerve ablation medical device 12may include a wire or conductive member 18 with a connector 20 that canbe connected to a connector 22 on the generator or controller 16 and/ora wire 24 coupled to the generator or controller 16. In at least someembodiments, the generator or the controller 16 may also be utilized tosupply/receive the appropriate electrical energy and/or signal toactivate one or more sensors disposed at or near a distal end of therenal nerve modulation medical device 12. When activated, the electrodesmay be capable of ablating tissue (e.g., renal nerves) as describedbelow and the sensors may be used to sense desired physical and/orbiological parameters.

FIG. 2A is a side view illustrating a portion of the renal nerveablation device 12. Here it can be seen that device 12 may include atubular member or catheter shaft 26. An expandable member 28 may becoupled to catheter shaft 26 (e.g., the elongate catheter shaft 26 mayhave a distal region and the expandable member 28 may be coupled to thedistal region of the elongate catheter shaft 26). In at least someembodiments, the expandable member 28 may be an expandable balloon. Inother embodiments, the expandable member 28 may be and/or include abasket, a stent, a plurality of struts, or the like.

An electrode 30 or a plurality of electrodes 30 may be coupled to theexpandable member 28. In at least some embodiments, the electrode(s) 30may be ablation electrodes that are capable of delivering ablationenergy to a suitable target. For example, the electrodes 30 may becapable of delivering ablation energy to tissue positioned adjacent to ablood vessel such as renal nerves positioned adjacent to a renal artery.

A conductive member 32 may be coupled to each electrode 30. Theconductive member 32 may take the form of a conductive trace, aconductive wire, or the like. Conductive members 32 may be coupled to orbe a region of conductive member 18 and, ultimately, may be coupled togenerator or controller 16. Thus, a suitable energy (e.g., RF energy orother form of energy) may be delivered to the electrode 30 (e.g., anactive electrode 31) via the conductive member 32. Illustratively, anactive electrode 31 may be an electrode 30 actively receiving powerthrough the conductive member 32 connected thereto.

In some instances, a single conductive member 32 may be connected toeach of a plurality of electrodes 30, as shown in FIGS. 2A-7B. Thesingle conductive member 32 connected to its respective electrode 30 maybe capable of powering that respective electrode 30 to which theconductive member 32 is connected. When the electrode 30 is receivingpower through the conductive member 32 connected thereto, the electrode30 may be considered an “active electrode” 31. When the electrode 30 isnot receiving power through its respective conductive member 32, theelectrode 30 may be considered an “inactive electrode 33”.Illustratively, the active electrode 31 is an electrode 30 that emitsenergy and the inactive electrode 33 is an electrode 30 that dissipatesor disperses energy.

In instances where there are a plurality of electrodes 30 applied to theexpandable member 28 or one or more other features of the medical device12, one of the plurality of electrodes 30 may be an active electrode 31and the remaining electrodes 30 may be inactive electrodes 33. In suchinstances, and/or other instances, the inactive electrodes 33 may act asreturn or ground electrodes, which may reduce or eliminate the need fora dedicated ground electrode and electrodes 30. Through the eliminationof dedicated ground electrodes running to each electrode 30 and/ordedicated conductive member 32 return paths (e.g., second conductivemembers running to each electrode 30), a size, footprint, and/orcomplexity of a flex circuit or the electrode 30 and the conductivemember 32, themselves, may be reduced and simplified, respectively. As aresult, the reduced size of the flex circuits or the electrode 30 andthe conductive member 32 may reduce the chances of the medical device 12failing (e.g., the electrode 30 may delaminate from the flex circuit,etc.) during insertion, withdrawal, or re-insertion of the cathetershaft 26 and/or the expandable member 28 in a blood vessel.

Return or ground electrodes may be capable of being a return electricalpathway for the active electrode 31. As a result, energy may bedelivered to the active electrode 31 and the return or ground electrodemay be the return electrical pathway. For example, FIGS. 2B, 3B, 4B, and5B illustrates that energy 40 may be delivered to body tissue 50 (whichmay include renal nerves and/or other nerve tissue) from the activeelectrode 30 and then back to the return or ground electrodes (e.g.,inactive electrodes 33).

When there are a plurality of electrodes 30 applied to the medicaldevice 12, a single one of the plurality of electrodes 30 may be anactive electrode 31 and the remaining electrodes 30 may be inactiveelectrodes 33 acting as return or ground electrodes, as shown in FIGS.2A-5B for example, or one or more of the remaining electrodes 30 may beinactive electrodes 33. Over time (e.g., during a procedure), theelectrode 30 of the plurality of electrodes 30 that is the activeelectrode 31 may remain active and the one or more electrodes 30 thatare inactive electrodes 33 may remain inactive.

Alternatively, over time (e.g., during a procedure), the electrode 30 ofthe plurality of electrodes 30 that is the active electrode 31 maychange or switch. For example, where there is a first electrode 30 a, asecond electrode 30 b, a third electrode 30 c, and a fourth electrode 30d, as shown in FIGS. 2A and 2B, the first electrode 30 a may be theactive electrode 31 and one or more of the remaining electrodes 30 b-30d may be inactive electrodes 33 (e.g., all of the remaining electrodes30 b-30 d may be inactive electrodes 33). In the example, the activeelectrode 31 may be switched from the first electrode 30 a to one of theremaining electrodes 30 b-d. As shown in FIGS. 3A and 3B, for example,the second electrode 30 b may be the active electrode 31 and any one ofthe remaining electrodes 30 a, 30 c, 30 d may be the inactive electrodes33 (e.g., all of the remaining electrodes 30 a, 30 c, 30 d may be theinactive electrodes 33). As shown in FIGS. 4A and 4B, for example, thethird electrode 30 c may be the active electrode 31 and any one of theremaining electrodes 30 a, 30 b, 30 d may be the inactive electrodes 33(e.g., all of the remaining electrodes 30 a, 30 b, 30 d may be theinactive electrodes 33. As shown in FIGS. 5A and 5B, for example, thefourth electrode 30 d may be the active electrode 31 and any one of theremaining electrodes 30 a, 30 b, 30 c may be the inactive electrodes 33(e.g., all of the remaining electrodes 30 a, 30 b, 30 c may be theinactive electrodes 33).

The described order of which electrode 30 is an active electrode 31 andwhich electrode(s) 30 are inactive electrodes 33 is not required and anyelectrode 30 may be the active electrode 31 and any one or more of theremaining electrodes 30 may be inactive electrodes 31, as desired.Further, the numbering of the electrodes 30 (e.g., the first electrode30 a, the second electrode 30 b, the third electrode 30 c, the fourthelectrode 30 d, etc.) is used for clarity of description purposes and isnot meant to be limiting. Additionally, more or fewer than four (4)electrodes may be utilized, as desired.

In some instances, each of the plurality of electrodes 30 may be activefor an equal amount of time over defined (e.g., set) time period (e.g.,a determined time for ablating tissue). In one illustrative example,where there are four electrodes 30 a, 30 b, 30 c, and 30 d, eachelectrode 30 may be active for a quarter of a set time period andinactive for three quarters of the set time period. Alternatively, or inaddition, each of the plurality of electrodes 30 may be active for a settime period (e.g., ten (10) seconds, fifteen (15) seconds, twenty (20)seconds, etc.) before a different electrode 30 of the plurality ofelectrodes 30 becomes active.

In some illustrative instances, the conductive member 32 (e.g.,conductive traces) may be covered or coated with a coating 42 forconductive member insulation, protection, and/or for other purposes, asshown in FIG. 6. The coating 42 may be applied to the conductive traces32 in any manner. For example, the coating 42 may be applied to theconductive traces 32 through a deposition method or other applicationmethod, as desired. In some instances, the electrodes 30 and/or otherfeatures (e.g., temperature sensors 44) may be masked prior to applyinga coating to the conductive members 32 to facilitate ensuring theelectrodes 30 and/or other features are not covered by the coating 42.

The coating 42 may be any type of insulating material (e.g.,electrically and/or thermally insulating) and/or protective material. Insome instances, the coating 42 may be a single material or multiplematerials mixed together and/or applied to the medical device 12separately. In one example, the coating 42 may be a thermoplasticpolyurethane (TPU). In some instances, a single layer of coating 42 maybe applied to the medical device 12. Alternatively, or in addition,multiple layers of coating 42 may be applied to the medical device 12.Where multiple layers of coating 42 may be applied to the medicaldevice, the conductive members 32 may be stacked up at a proximal waistof the expandable member 28 (e.g., where the expandable member 28 meetsthe tubular member or catheter shaft 26).

In some illustrative instances, a non-conductive or insulator layer 34may be disposed adjacent to the conductive member 32. The electrode 30may be disposed along the non-conductive layer 34. The non-conductivelayer 34 may insulate the electrode 30 and/or the conductive member 32from other structures including conductive structures along theexpandable member 28 (e.g., which may include one or more conductivemembers/electrodes acting as ground electrodes).

In some instances, the electrode(s) 30 may be disposed along a flexiblecircuit 46 (e.g., a “flex circuit”), as shown in FIGS. 7A and 7B. Someexample flex circuits that may be utilized for device 12 (and/or otherdevices disclosed herein) may include or otherwise be similar to flexcircuits disclosed in U.S. patent application Ser. No. 13/760,846, theentire disclosure of which is herein incorporated by reference. In oneexample flex circuit 46, the flex circuit 46 may include one or morepolymeric layers (e.g., the insulation layer 34), such as polyimide orother polymeric layers with electrode(s) 30 and conductive member(s) 32coupled thereto.

A flex circuit 46 may include a single electrode 30 and a singletemperature sensor 44 applied to the insulation layer 34 and one or moreflex circuits 46 may be applied to the expandable member 28.Alternatively, or in addition, a flex circuit 46 may include a pluralityof electrodes 30 and one or more temperature sensors 44 applied to theinsulation layer and one or more flex circuits 46 may be applied to theexpandable member 28, as shown in FIGS. 7A and 7B. In other instances,the electrode 30 may be disposed along a printed circuit applied to theexpandable member 28 or placed on a strut of a basket (e.g., where thebasket is an expandable member 28) and attached to a conductive wire(e.g., where the conductive wire is a conductive member 32).

In some instances, one or more temperature sensor 44 may be coupled tothe expandable member 28 and/or the flex circuit. The temperaturesensors 44 may include a thermistor, thermocouple, or any other suitabletemperature sensor. In some cases, a conductive member 36 may be coupledto the temperature sensor 44. As shown in FIGS. 2A, 3A, 4A, 5A, 6, and7A, a single conductive member 36 may be coupled to each temperaturesensor 44. Illustratively, the conductive member 36 coupled to thetemperature sensor 44 may be the same as or different than theconductive member 32 coupled to the electrode 30. For example, theconductive member 32 may take the form of a conductive trace, aconductive wire, or the like, which may be capable of and/or configuredto transmit electrical signals and/or electrical power to and from thetemperature sensor 44.

In some instances, the conductive traces 36 may be covered or coatedwith a coating 42 for conductive member insulation, protection, and/orfor other purposes. The coating 42 may be applied to the conductivetraces 36 in any manner. For example, the coating 42 may be applied tothe conductive traces 36 through a deposition method or otherapplication method, as desired. In some instances, the temperaturesensors 44 and/or other features (e.g., electrodes 30) may be maskedprior to applying a coating to the conductive members 32 to facilitateensuring the temperature sensors 44 and/or other features are notcovered by the coating 42.

The coating 42 may be any type of insulating (e.g., electrically and/orthermally insulating) and/or protective material. In some instances, thecoating 42 may be a single material or multiple materials that may bemixed together and/or applied to the medical device 12 separately. Inone example, the coating 42 may be a thermoplastic polyurethane (TPU).In some instances, a single layer of coating 42 may be applied to themedical device 12. Alternatively, or in addition, multiple layers ofcoating 42 may be applied to the medical device 12. Where multiplelayers of coating 42 may be applied to the medical device, theconductive members 32 may be stacked up at a proximal waist of theexpandable member 28 (e.g., where the expandable member 28 meets thetubular member or catheter shaft 26.

In use, as shown in FIG. 8, the renal nerve modulation system 10 may beutilized in a method 100 for ablating renal nerves or in other ablationmethods. In one example, the method 100 may include providing 102 amedical device, such as the renal nerve ablation medical device 12. Theprovided medical device 12 may include the elongate shaft (e.g., thetubular member or catheter shaft 26) having a distal end and/or regionand an expandable member 28 coupled to the distal region of the cathetershaft 26. Further, in some instances, two or more (e.g., a plurality) ofthe electrodes 30 may be coupled to the expandable member 28 and aplurality of conductive members 32 (e.g., conductive traces) may becoupled to the elongate catheter shaft 26 or expandable member 28, wherea single conductive member 32 may be connected to each of the two ormore electrodes 30.

The method 100 may include advancing 104 the provided medical device 12through a blood vessel (e.g., the aorta A or other blood vessel) to aposition within the renal artery RA or other vessel and expanding 106the expandable member 28 and placing the expandable member 28 adjacentor near a target tissue. Once the expandable member 28 has beenexpanded, one of the electrodes 30 may be activated 108. Whileactivating 108 the one electrode 30 to create an active electrode 31,the remaining electrodes 30 may be maintained 110 as inactive to formground electrodes. In some instances, the active electrode 31 may bedeactivated 112 and one of the other electrodes 30 (e.g., inactiveelectrodes 33) may be activated 114 to form an active electrode, suchthat a different one of the two or more electrodes 30 is active and theremaining electrodes, including the electrode 30 that was formerly theactive electrode 31 may now be inactive electrodes 33. The deactivatingan active electrode 31 and activating an inactive electrode 33 may beoptional, as depicted in FIG. 8 with a dotted box.

In some instances, the activation and/or deactivation of electrodes 30may be manually controlled or automatically controlled through one ormore activation or deactivations devices. In one example, the generatoror controller 16 may be utilized to manually and/or automaticallycontrol which electrode 30 is the active electrode. The generator orcontroller 16, which may include or communicate with a processor and amemory, may activate and deactivate electrodes 30 with the processorbased on a computer program stored in its memory for a particularprocedure. The program utilized by the generator or controller 16deactivate or activate an electrode 30 after a set time period, after atemperature of a body tissue 50 or other feature is achieved, or anyother criteria is achieved. In some cases, the program utilized by thegenerator or controller 16 may be manually overridden by a user and auser may manually dictated which electrode(s) 30 are active (e.g., oneor more electrode 30 may be active electrodes 31 and/or one or moreelectrode 30 may be inactive electrodes 33). The electrodes 30 may beactivated or deactivated via the generator or controller 16 in anymanner, as desired.

In one example, the two or more electrodes may include the firstelectrode 30 a, the second electrode 30 b, the third electrode 30 c, andthe fourth electrode 30 d. Illustratively, one of the electrodes 30 a-30d may be activated (e.g., the first electrode 30 a) to form an activeelectrode 31 and the remaining electrodes 30 (e.g., the second electrode30 b, the third electrode 30 c, the fourth electrode 30 d) may beinactive electrodes 33 and act as ground electrodes. Then, after a firstperiod of time (e.g., one second, two seconds, five seconds, tenseconds, fifteen second, thirty seconds, one minute, two minutes, fiveminutes, etc.) the active electrode 31 (e.g., the first electrode 30 a)may be deactivated, another electrode 30 (e.g., the second electrode 30b) may be activated to form an active electrode 31, and the remainingelectrodes 30 (e.g., the first electrode 30 a, the third electrode 30 c,and the fourth electrode 30 d) may be maintained as inactive electrodes33 to form ground electrodes. Further, after a second period of time,which may be the same as the first period of time or any other amount orperiod of time, the active electrode 31 (e.g., the second electrode 30b) may be deactivated, another electrode 30 (e.g., the third electrode)may be active to form an active electrode 31, and the remainingelectrodes 30 (e.g., the first electrode 30 a, the second electrode 30b, and the fourth electrode 30 d) may be maintained as an inactiveelectrode 33 to form ground electrodes.

The method 100 of switching which electrode(s) 30 are active may go onfor any period or length of time. In one example, this method maycontinue and/or may repeat itself until a renal nerve modulationprocedure or any other ablation procedure or a portion thereof iscompleted. In some instances, each electrode 30 of the medical device 12will be an active electrode for a set period of time, where the setperiod of time for each electrode 30 may be the same as the set periodof time for each electrode 30, may be different from a set period oftime for at least one electrode 30, or may be different from the setperiod of time of all other electrodes 30. Alternatively, or inaddition, an electrode 30 may remain the active electrode 31 until bodytissue 50 adjacent the active electrode 31 reaches a thresholdtemperature as measured by a temperature sensor 44 associated with theactive electrode 31 or a different temperature sensor 44, as desired.

The materials that can be used for the various components of device 12(and/or other devices disclosed herein) may include those commonlyassociated with medical devices. For simplicity purposes, the followingdiscussion makes reference to device 12. However, this is not intendedto limit the devices and methods described herein, as the discussion maybe applied to other similar tubular members and/or components of tubularmembers or devices disclosed herein.

Device 12 and the various components thereof may be made from a metal,metal alloy, polymer (some examples of which are disclosed below), ametal-polymer composite, ceramics, combinations thereof, and the like,or other suitable material. Some examples of suitable polymers mayinclude polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions device of 12 may also be dopedwith, made of, or otherwise include a radiopaque material. Radiopaquematerials are understood to be materials capable of producing arelatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of device 12 in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofdevice 12 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility may be imparted into device 12. For example, portions ofdevice, may be made of a material that does not substantially distortthe image and create substantial artifacts (i.e., gaps in the image).Certain ferromagnetic materials, for example, may not be suitablebecause they may create artifacts in an MRI image. In some of these andin other embodiments, portions of device 12 may also be made from amaterial that the MRI machine can image. Some materials that exhibitthese characteristics include, for example, tungsten,cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®,PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g.,UNS: R30035 such as MP35-N® and the like), nitinol, and the like, andothers.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for performing ablationprocedures, comprising: an elongate shaft having a distal region; anexpandable member in the form of an expandable balloon having acylindrical central portion coupled to the distal region; a plurality ofelectrodes comprising at least four electrodes coupled to the expandablemember; a conductive member connected to each of the electrodes, whereeach of the connected conductive members is capable of supplying powerto the electrode to which the conductive member is connected; and acontroller connected to each of the conductive members; wherein thecontroller is configured to activate each of the plurality of electrodesby supplying power to each of the plurality of electrodes; and whereinthe controller is configured such that when the controller activates oneof the plurality of electrodes by supplying power to one of theplurality of electrodes, the controller automatically maintains all ofthe remaining unpowered electrodes as inactive so as to act as groundelectrodes.
 2. The medical device of claim 1, further comprising: one ormore temperature sensors coupled to the expandable member; and a singleconductive member connected to each of the one or more temperaturesensors.
 3. The medical device of claim 1, wherein the conductive memberis a conductive trace.
 4. The medical device of claim 1, wherein the oneof the plurality of electrodes that is activated changes over time. 5.The medical device of claim 1, wherein each of the plurality ofelectrodes is activated for an equal amount of time.
 6. The medicaldevice of claim 1, further comprising: a coating of insulating materialcovering each of the conductive members.
 7. The medical device of claim6, wherein the coating comprises a thermoplastic polyurethane (TPU). 8.The medical device of claim 6, wherein the coating comprises a pluralityof layers of material.
 9. The medical device of claim 1, wherein theballoon is configured to be advanced through a blood vessel to aposition within a renal artery and subsequently expanded in the renalartery.
 10. The medical device of claim 1, wherein the plurality ofelectrodes comprises more than four electrodes.
 11. A medical device forrenal nerve ablation, comprising: an elongate shaft having a distalregion; an expandable balloon having a cylindrical central portioncoupled to the distal region, wherein the balloon is configured to beadvanced through a blood vessel to a position within a renal artery andexpanded in the renal artery; a plurality of electrodes comprising fourelectrodes coupled to the balloon; and a plurality of conductive tracescoupled to the elongate shaft, where a single conductive trace of theplurality of conductive traces is connected to each of the electrodessuch that each of the connected single conductive traces is capable ofsupplying power to the electrode to which the single conductive trace isconnected; and a controller connected to each of the conductive traces,wherein the controller is configured to activate each of the pluralityof electrodes by supplying power to each of the plurality of electrodes;wherein the controller is configured such that when the controlleractivates one of the plurality of electrodes by supplying power to oneof the plurality of electrodes, the controller automatically maintainsall of the remaining plurality of electrodes as inactive so as to act asa ground electrode.
 12. The medical device of claim 11, furthercomprising: a flex circuit disposed along the balloon; and wherein atleast one of the plurality of electrodes is disposed along the flexcircuit.
 13. The medical device of claim 11, further comprising: aplurality of temperature sensors coupled to the balloon; and a singleconductive trace connected to each of the plurality of temperaturesensors.
 14. The medical device of claim 11, wherein the plurality ofelectrodes comprises more than four electrodes.
 15. A method forablating renal nerves, the method comprising: advancing the medicaldevice of claim 1 through a blood vessel to a position within a renalartery; expanding the expandable member; activating one of the pluralityof electrodes; and automatically maintaining all of the remainingelectrodes of the plurality of electrodes as inactive so as to functionas ground electrodes, thereby performing renal nerve ablation.
 16. Themethod of claim 15, further comprising: deactivating the one activatedelectrode of the plurality of electrodes; and activating another of theplurality of electrodes.
 17. The method of claim 15, wherein the fourelectrodes correspond to a first electrode, a second electrode, a thirdelectrode, and a fourth electrode; wherein the first electrode is theone of the plurality of electrodes activated; and the second electrode,the third electrode, and the fourth electrode are inactive electrodesand act as ground electrodes; and wherein the method further comprises:deactivating the first electrode after a first period of time;activating the second electrode; automatically maintaining the firstelectrode, the third electrode, and the fourth electrode as inactive toact as ground electrodes; deactivating the second electrode after asecond period of time; activating the third electrode; automaticallymaintaining the first electrode, second electrode, and the fourthelectrode as inactive to act as ground electrodes; and deactivating thethird electrode after a third period of time; activating the fourthelectrode; and automatically maintaining the first electrode, secondelectrode, and the third electrode as inactive to act as groundelectrodes.
 18. The method of claim 17, wherein the first period of timeis substantially equal to one or more of the second period of time andthe third period of time.
 19. The method of claim 17, wherein eachperiod of time is different than each other period of time.
 20. A methodfor ablating renal nerves, the method comprising: advancing the medicaldevice of claim 11 through a blood vessel to a position within a renalartery; expanding the expandable balloon; activating one of theplurality of electrodes; and automatically maintaining the remainingelectrodes of the plurality of electrodes as inactive so as to functionas ground electrodes, thereby performing renal nerve ablation.